Technology update

Apr 23, 2007

Ceramic fibres reach the nanoscale

Material scientists in the US and Spain have invented a new technique called "laser spinning" to produce very long amorphous nanofibres that are several centimetres long, but just 35 nm across. The breakthrough advance could allow near-continuous fibres with tailored compositions to be made.

Quasi-one-dimensional structures such as nanowires, nanobelts, nanorods and nanotubes have unique electrical and mechanical properties. They look set to revolutionize fields as diverse as electronics, catalysis, sensing, composite materials and biomedicine. At present, these structures are typically produced by vapour phase or solution-based growth. Scientists would also like to make continuous lengths of these materials on the nanoscale, as this would be a major technical and economic advance. However, at present they are only able to produce micron-sized fibres using several techniques that rely on elongating a molten viscous batch of precursor material.

Juan Pou and colleagues at the University of Vigo and Adrian Mann and co-workers at Rutgers University have now overcome this problem. The researchers have produced very long amorphous nanofibres in a simple physical process that does not involve catalysts, templates or any other reagents except the precursor material with the desired fibre composition. Not only does the method produce nanosized fibres, it can also produce nanofibres directly from materials that melt at high temperatures – something that is not possible with other similar techniques, such as electrospinning.

Laser spinning essentially involves using a high-power laser to make a cut in a plate of the precursor ceramic material, such as silica or alumina. This novel approach ensures that only a small volume of ceramic is in the fluid state – at the melt front (the leading edge of the cut) – at any one time. While this is being done, a supersonic nozzle injects a high-velocity gas jet in the area of the cut. The viscous molten material produced is then quickly stretched and cooled by the gas jet in a simple elongation process, to yield a disordered net of intertwined amorphous micro- and nano-fibres (see figure).

"This advance is exciting because the physical (rather than chemical) nature of this technique allows the production of very long amorphous nanofibres with tailored compositions," lead author Félix Quintero told nanotechweb.org. "Some likely applications of these nanofibres include nanocomposites, nano-templating, tissue engineering, sensors, and new types of fabrics."

The team is now working on better controlling the process and making new compositions.